Synthesis of accelerations of the 1976 Tangshan earthquake(M_S 7.8)in near-and far-field by using semi-empirical method

In this paper a heterogeneous fault model of the Tangshan earthquake is suggested, which consists of two southern sub faults striking N30°E and two northern sub faults striking N50°E. Total length of the main shock fault is 114 km and seismic moment is about 1.4×10 20 N·m. The epicentre of the main shock is located at the southern part, near the intersection of the two bands. Accelerations of two aftershocks ( M L 5.5, M S 6.9 ) were used as empirical Green's functions to synthesize the accelerations of the main shock in near and far field. A method that small events and main shock are considered not satisfying the similarity relationship in the improved empirical Green's function is also applied in this paper. Peak values, duration and response spectra of synthesized accelerations in far field are in agreement with the observed records. The synthesized results in near field are also in agreement with the epicentral intensity distribution of the main shock. The results show that the peak acceleration of Tangshan earthquake in epicentral region exceeds 1.1 g. It is consistent with the peak accelerations recorded in some large earthquakes occurred in recent years.

Simulation of strong earthquake characteristics of a scenario earthquake(M_(S)7.5)based on the enlightenment of 2022 M_(S)6.9 earthquake in Menyuan

The Menyuan area is an important transportation hub in the Hexi Corridor.The Menyuan M_(S)6.9 earthquake that occurred on January 8,2022 had a major impact on the local infrastructure and transportation of this region.Due to the high possibility of similar strong earthquakes occurring in this area in the future,preliminary assessment of the seismic intensity characteristics of destructive earthquakes in this region is essential for effective disaster control.This paper uses the empirical Green′s function(EGF)method as a numerical simulation tool to predict the ground motion intensity of Datong Autonomous County under the action of the scenario earthquake(M_(S)7.5).Seismic records of aftershocks of the 2016 Menyuan M_(S)6.4 earthquake were used as Green’s functions for this simulation.The uncertainties associated with various source parameters were considered,and 36possible earthquake scenarios were simulated to obtain 72 sets of horizontal ground motions in Datong County.The obtained peak ground acceleration(PGA)vs.time histories of the horizontal ground motion were screened using the attenuation relationships provided by the fifth-edition of China’s Seismic Ground Motion Parameter Zoning Map and the NGA-West2dataset.Ultimately,32 possible acceleration-time histories were selected for further analysis.The screened PGA values ranged from 78.8 to 153 cm/s^(2).The uncertainty associated with the initial rupture point was found to greatly affect the results of the earthquake simulation.The average acceleration spectrum of the selected acceleration-time history exceeded the expected spectrum of a intermediate earthquake,which means that buildings in Datong County might sustain some damage should the scenario earthquake occur.This research can provide reliable ground motion input for urban earthquake damage simulation and seismic design in Datong County.Growing the dataset of small earthquakes recorded in this region will facilitate the large-scale simulation of ground motions under different earthquake scenarios.